BACKGROUND: This study aimed at comparing air-sealing characteristics of the new tapered-shaped tracheal tube cuffs with cylindrical tube cuffs.
METHODS: Tracheal tubes with tapered-shaped polyurethane (PU) and polyvinyl chloride (PVC) cuffs as well as standard cylindrical-shaped cuffs made of PU and PVC (Covidien, Athlone, Ireland) were investigated. A tracheal model attached to a test lung was intubated, and cuffs were inflated to 10, 15, 20, 25 and 30 cm H(2)O. The test lung was ventilated with intermittent positive pressure ventilation at peak inspiratory pressures (PIPs) of 20 and 25 cm H(2)O. Air leakage was assessed by spirometry and measurement of sevoflurane concentration passing the cuff at the upper cuff border using an anaesthetic gas analyser. Experiments were repeated four times with new tracheal tubes for each run. Statistical comparisons were done using Mann-Whitney U-test with level of significance at P < 0.05.
RESULTS: The tapered-shaped PVC tube cuff demonstrated a significantly lower air leakage determined by spirometry than the cylindrical-shaped cuff at both PIPs (20 and 25 cm H(2)O). Similarly, sevoflurane leakage was less with the tapered PVC cuff particularly at higher cuff pressures. With the PU cuff, reduction in air leakage by a tapered-shaped compared with a cylindrical-shaped tube cuff was not significant.
CONCLUSIONS: A tapered-shaped tube cuff considerably improves air-sealing characteristics of PVC tube cuffs and allows thereby reducing cuff pressure required for sufficient ventilation. In tube cuffs made of PU that exhibits superior sealing characteristics compared with PVC, a tapered shape failed to result in a further reduction of air leakage.